Ozone and diesel emissions from trucks and generators used on movie sets as well as pyrotechnic explosions for special effects contribute to the layer of smog that hangs over Los Angeles.

"Many industries are moving toward more environmentally sustainable operations, and it's important that we monitor their progress," says institute director and law professor Mary Nichols.

Nichols says researchers note that although several studios and production companies are taking steps to minimise damage, the industry's lack of a unified environmental strategy is a barrier to improvement.

Two UCLA professors who conducted an analysis as part of the study conclude that Hollywood could be doing more, the report says.

"Our overall impression is that, with a few notable and inspiring exceptions, environmental considerations are not high on the agenda in the film and television industry, and that more could be done within the industry to foster environmentally friendly approaches," the professors say.

The researchers cite the example of the makers of The Day After Tomorrow, who paid for a US$200,000 (A$260,000) package of environmental measures to offset damage caused by vehicles used in the 2004 blockbuster.

The makers of the last two Matrix films were also praised for arranging for more than 97% of set materials to be recycled.

The study found the problem is attributable to the transient nature of production companies.

"The degree to which work is controlled by short-lived ever-changing production companies ... [makes] it difficult to institutionalise best practices," it says.

Business groups warn against using the report to crack down on the film and television industry, which generates around US$29 billion a year in combined revenues and employs around 252,000 people.